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George Weiblen

University plant biologist George Weiblen, lead organizer of the Evolution 2008 conference, says there has been no more exciting time to be an evolutionary biologist than today.

An evolving science

The Evolution 2008 conference celebrated a vibrant field

By Deane Morrison

June 30, 2008

On a balmy summer night, lawns come alive with the cricket version of "American Idol," as each male "sings" in an effort to convince the local females to pick him. In the air, male fireflies flash to advertise their virility, looking for a female to signal by flashing back. Besides being delightful, these ordinary mating displays illustrate some of the myriad facets of evolution that took center stage in the Evolution 2008 conference, held at the University of Minnesota in Minneapolis June 20-24. It was held here "because we have a critical mass of evolutionary biologists at the University," says George Weiblen, an associate professor of plant biology and lead conference organizer. "It was an opportunity to showcase our talents and bring hot science to our doorstep. It's the largest meeting of evolutionary biologists in the world." More than 1,400 biologists from 22 countries, including 69 University faculty and students, presented their research and ideas.

Siren songs, flagrant flashers, diabolical deceit

In Hawaii, new species of crickets are rapidly evolving, said Cornell University researcher Chris Wiley. But as new species arise, they have to avoid interbreeding in order to remain separate. The best way to keep separate is for males to evolve new songs (or chirps), and for the females to evolve a preference for that song at the same time. But why should both the song and the preference for it evolve at the same time? It seems like a too convenient coincidence. But maybe not.

"When we have a predator-prey system or a host-parasite system, we have a co-evolutionary arms race where the prey is under pressure to come up with new ways of eluding the predator, then the predator adapts."

It could be, said Wiley, that changes--called mutations--in a single gene or group of genes could be responsible. In a male, the change results in a new song, while in the female the change confers a preference for that song. Sometimes, one gene can produce different traits in males and females, and Wiley and his colleague Kerry Shaw are investigating whether this is happening in the crickets. A recurring question in evolutionary biology is how new versions of old genes arise in the first place. Researcher Yuichi Oba (Nagoya University, Japan) reported on his studies of genes found in fireflies and other beetles; his work suggests a likely way in which genes for the flashing ability first appeared and then diversified, resulting in different flashing patterns in different firefly species.

A new look at the history of evolution

The theory of evolution has had its share of both fans and critics over the centuries. In a new book, "More Than Darwin: An Encyclopedia of the People and Places of the Evolution-Creationism Controversy (Greenwood Press, 2008)," University authors Randy Moore and Mark D. Decker lay out the life and times of one of the greatest ideas in all science, with sketches of the often colorful characters who promoted or condemned it. Moore is the H.T. Morse-Alumni Distinguished Teaching Professor of Biology and Decker is associate director for scholarship and teaching in the Biology Program.

Listen to an interview with Randy Moore about writing the book.

The firefly owes its flash to an enzyme known as luciferase, which carries out a chemical reaction that produces light. Oba found intriguing similarities in genes for luciferase and genes for an enzyme that metabolizes fatty substances; this second enzyme is found in both fireflies and related beetles. Most probably, said Oba, a genetic error occurred long ago in a beetle. That error caused the gene for the fat-metabolizing enzyme to be duplicated. The extra copy of the gene that could then mutate without harming the original gene's function. As the beetle's descendants multiplied, the extra gene mutated into the gene for luciferase, and fireflies were born. But evolution doesn't stop. As befits insects with an enzyme named for Lucifer, some fireflies have evolved the ability to put their flashes to diabolical use. Certain females can mimic the flashing patterns of females of other species. On seeing those flashes, amorous males of the other species fly straight to the source, where they are promptly devoured.

The better to kill you with, my deer

A study of wolves in Yellowstone Park led by University postdoc Daniel MacNulty shows that as predators evolve to take the prey available, sizing themselves can be a tricky thing. "Species within lineages tend to evolve into larger sizes," said MacNulty, using the diminutive ancestors of modern whales, horses, and elephants as examples. "Bigger predators chase bigger prey, but bigger size can slow them down." The Yellowstone wolf packs used different skills to bring down elk, MacNulty reported. First they rush the herd, then they select an individual and separate it from its fellow elk, and finally they wrestle it to the ground and kill it. Rushing doesn't seem to require any particular size, MacNulty said, but closing in on the chosen victim requires a burst of speed, which would be hampered by too much body weight. Conversely, pulling the elk down is a job for burly wolves. In fact, MacNulty and his colleagues found that a wolf's chances of successfully separating an elk out from the herd rose only until the wolf reached about 86 pounds, then leveled off. But the chances of wrestling down and killing an elk didn't level off, suggesting that large size is favored for this job. Size is a tradeoff; male lions, for instance, are bigger than females and worse at chasing prey but better at killing, he said. In general, small carnivores, such as cheetahs, are adapted to running while large ones, such as polar bears, are built for grappling. According to fossil evidence, "extinctions of American lions [larger Ice Age cousins of sabretooth cats] may suggest they couldn't shift from larger, slow prey [like mammoths, which went extinct] to smaller, faster prey," said MacNulty.

The Red Queen lives

In Lewis Carroll's "Through the Looking Glass," Alice meets the Red Queen, who must run as fast as she can just to stay in place. The Red Queen has been adopted as a metaphor by some evolutionary biologists to illustrate how predators and prey have to keep up with each other. "When we have a predator-prey system or a host-parasite system, we have a co-evolutionary arms race where the prey is under pressure to come up with new ways of eluding the predator, then the predator adapts," says Weiblen. "A good example of the Red Queen is the pharmaceutical industry and infectious bacteria. New antibiotics like streptomycin come along, and bacteria evolve resistance." A strong driving force in such systems is natural selection, which means that bacteria in which antibiotic-resistance genes appear will be "selected" to live and give rise to the next generation Given that, plus numerous observations that people differ considerably in their resistance to disease, their response to drugs, and other traits, Weiblen calls on the University to add evolutionary biology to its Medical School curriculum. "The ability to care for our bodies is enhanced by knowing our history as a species," he says. "The medical profession isn't aware of evolutionary biology's potential for making them better doctors," adds Scott Lanyon, director of the University's Bell Museum of Natural History. "Evolutionary biologists in general feel strongly [that there's a real need to integrate evolutionary biology into medical curricula."